This is a request for a flexible, modular system for confocal scanning microscopy of cells and tissues. The system takes advantage of several recent advances in optical microscopy techniques, and will allow for integration of future methods as they become available. Based on proven technology already in use in our core facility, the Zeiss LSM 510 system includes robust, user-friendly software for instrument control and data processing. Acquisition, processing, storage and visualization, as well as extensive quantitation, can be easily carried out on confocal optical sections, volume data sets, and time-lapse series. With added features such as spectral analysis and automated x-y stage movement, the system will make the most modem optical microscopy techniques available to all members of the user group and to others at the University. The users have extensive expertise in light and electron microscopy and find that in most cases, confocal microscopy is the method of choice for imaging biological material in three dimensions (e.g. within tissue sections, embryos, cell aggregates or round cells). Time-lapse imaging and optical sectioning will be applied to a wide range of biological systems including cell migration, cell polarity, organelle motility, cytoskeletal rearrangements during cell division and differentiation; and pattern formation, signal transduction, and protein expression during development. In all cases, a strong emphasis is placed on the molecular mechanisms (e.g. signal transduction events, post-translational protein modification, and the role of specific elements of the cytoskeleton) in these cellular processes. These projects will also develop better methods to combine optical microscopy with yeast and Dictyostelium genetics. Although virtually every member of the user group has a conventional microscope and access to a confocal microscope, none has sufficient access to confocal imaging systems. Therefore, the requested equipment will enhance the user group's ability to complete projects underway, allow new projects to be initiated, and avoid duplication of effort and expense. Finally, since availability of compatible fluorescent probes often limits experimental options, the spectral analysis capabilities of this system will greatly expand the universe of possible investigations. The instrument will be incorporated into a well-managed existing core facility, directed since its inception in 1997 by the P.I. As an integral component of our Optical Microscopy Facility, the instrument will be accessible to members of the user group and others throughout the University, promoting collaboration and exchange of ideas.